JPS62240449A - Device for controlling fuel injection rate - Google Patents

Abstract

PURPOSE:To adjust an injection suspending period to the optimum value by providing a piezo-actuator being faced to a high pressure chamber and charging said actuator up to an operated voltage value in accordance with an operating condition while discharging said actuator at a certain time. CONSTITUTION:A piezo-actuator 3 to which a piezo-electric effect is adapted, is installed being faced to the high pressure chamber 12 which can be pressurized by means of a plunger 11, of a distribution type ported pump 1. This actuator 3 is charged with electric charge by a piezo-charging means 6 while, on the other hand, a charge which is built up in the piezo-actuator 3 is discharged by a piezo-discharging means 7. The charging means 6 and the discharging means 7 are controlled by a microcomputer 5 in accordance with the output of an operating condition detecting means 4 including the detectors 41-43 of engine speed, engine load, and cooling water temp., etc. Thereby, a pilot injection by means of the injection pump 1 can be realized, while always adjusting a fuel injection suspending period to be the optimum.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel injection system having a mechanism for performing pilot injection prior to main injection of fuel in order to reduce noise and vibration of a diesel engine, for example, when idling. Relating to a rate control device.

[Conventional technology]

Conventional pilot injection methods include two plungers for pumping fuel that are driven separately, two fuel injection nozzles that perform pilot injection and main injection with each nozzle, and even fuel injection. There is one that has two levels of nozzle opening pressure.

Among the above-mentioned conventional techniques, the method using two plungers or nozzles has the disadvantage that the drive means becomes complicated and the device becomes large. Further, in the case where the valve opening pressure is set in two stages and pilot injection and main injection are performed separately, the nozzle becomes large and difficult to attach to the engine.

Also, as shown in Japanese Patent Application Laid-Open No. 59-18249,
A pump has been proposed in which fuel rate control including pilot injection is performed by applying a voltage to a piezo stack installed in a high pressure chamber of a pump to expand and contract the piezo stack.

[Problem that the invention seeks to solve]

Among the conventional technologies mentioned above, those using piezo elements have a simple piezo actuator structure and are small and lightweight, but on the other hand, it is difficult to adjust the interval between pilot injection and main injection of fuel (hereinafter referred to as "injection stop period"). The injection stop period must be set to an appropriate value.

Problems arise because the ignitability of fuel during main injection deteriorates.

Therefore, the present invention activates a piezo actuator to realize pilot injection by an injection pump, and optimizes the fuel injection stop period according to the signal from the operating state detection means that detects at least the rotation speed of the diesel engine according to the first invention. According to the second invention, it is an object of the present invention to provide a fuel injection rate control device for a diesel engine that optimizes the fuel injection stop period and viroft injection amount according to a signal from an operating state detection means. There is.

[Means for solving problems]

In order to achieve the above object, a first invention detects the operating state of a diesel engine and a piezo actuator installed facing a high pressure chamber of a fuel injection pump, and detects at least the rotational speed of the diesel engine. a driving state detecting means for detecting a driving state; a charging voltage calculating means for calculating a voltage value to be charged to the piezo actuator according to a signal from the driving state detecting means; This configuration includes a piezo charging means for charging the actuator, and a piezo discharging means for discharging the electric charge generated in the piezo actuator at a predetermined time.

The second invention also includes a piezo actuator mounted facing the high pressure chamber of a fuel injection pump, and an operating state detecting means for detecting at least the rotational speed of the diesel engine. , charging voltage calculating means for calculating a voltage value to be charged to the piezo actuator according to a signal from the operating state detecting means;
piezo charging means for charging the piezo actuator to a voltage value calculated by the charging voltage calculation means; and calculating a discharge timing for discharging the electric charge generated in the pinisge actuator according to a signal from the operating state detection means. This configuration includes a discharge time calculation means and a piezo discharge means for discharging the electric charge generated in the piezo actuator at the discharge time.

[Effect]

With the above configuration, the first invention determines the amount of charge to be charged to the piezo actuator according to the operating state of the diesel engine, and discharges the charge generated in the piezo actuator at a predetermined time. The interval between pilot injection and main injection of fuel is adjusted by the voltage difference between the terminals of the piezo actuator.

In the second invention, the amount of electric charge to be pre-charged to the piezo actuator and the timing to discharge the electric charge generated in the piezo actuator are determined according to the operating state of the diesel engine, and the piezo actuator is activated at the time of discharge determined according to the amount of electric charge that is pre-charged. The injection stop period is adjusted by the terminal voltage difference, and the pilot injection amount is simultaneously adjusted by adjusting the discharge timing.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the fuel injection rate control device of the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. In the figure, 1 is a Bosch type distribution type fuel injection pump, and 11 is a plunger, which is pushed to the left in the figure by a face cam (not shown) to make the fuel in the high pressure chamber 12 high pressure, and from the nozzle 2 (not shown). It injects fuel into the combustion chamber of a diesel engine. A piezo actuator 3 is mounted facing the high pressure chamber 12 and utilizes a piezo voltage effect. This piezo actuator 3 is, for example,
The structure is as disclosed in Japanese Patent No. 9-18249.

Reference numeral 4 denotes an operating state detection means, which includes at least a rotation speed detector 41 that detects the rotation speed of the diesel engine, an engine load detector 42 such as an accelerator sensor that detects the load of the diesel engine, and a cooling device for the diesel engine. It consists of a cooling water temperature detector 43 and the like that detect the temperature of water, and outputs signals from these to the microcomputer 5. 5 is a microcomputer, CPU51,
It incorporates a memory 52, a timer 53, an A/D converter 54, etc. This microcomputer 5 has the functions of a charging voltage calculating means and a discharging time calculating means in the present invention, and as will be described later, in this embodiment, the amount of charge to be charged to the piezo actuator 3 in advance is divided into multiple times. It also has a function to calculate the number of times it is charged. 6 is a piezo charging means, which includes an inductor 61 for charging the piezo actuator 3, a battery (not shown), the inductor 61, and the piezo actuator 3.
Transistor 6 for transferring energy
2, and a diode 63 to prevent the energy stored in the piezo actuator 3 from returning to the battery via the inductor 61. 7 is a piezo discharge means, which is composed of a transistor 71 for discharging the electric charge generated in the piezo actuator 3, and a resistor 72 for limiting the current and protecting the transistor 71.

FIG. 2 shows a schematic diagram representing the charging voltage calculation means.

A three-dimensional map interpolation calculation programmed into the microcomputer 5 calculates the target charging voltage 100 according to signals from the rotational speed detector 41, engine load detector 42, cooling water temperature detector 43, and the like. The three-dimensional map data that is the subject of this interpolation calculation is based on diesel engine compliance standards, so it cannot be generalized, but as will be explained later, the voltage to pre-charge the piezo actuator 3 and the injection stop period are proportional to each other. Because of the relationship, when the cooling water temperature is low, the ignition delay of the pilot injection is large, so the charging voltage is increased. It is desirable to use manbu data that reduces the charging voltage.

FIGS. 3(al, bl, and c) are timing charts showing the operation of the piezo charging means 6. First, when the transistor 62 is turned on, current begins to flow through the inductor 61, and after a time T. , IM = Va X TON/L --
-1) current l14 flows. (Here, ■, :Ha・
7teri voltage, L: inductance of inductor 61),
Then, the transistor 62 becomes "OFF", and all the energy stored in the inductor 61 is transferred to the piezo actuator 3, and the piezo is charged. . C7, time. 8 is arbitrarily adjusted to a constant value such that the current IN does not exceed the rated current of the transistor 62 in (11).

Then time T. 1. transistor 6 again after
2 is turned on, and charging of the piezo actuator 3 is repeated N times in the same way. Here, the time T or F may be longer than the time required for all the energy of the inductor 61 to be transferred to the piezo actuator 3. At this time, the voltage V across the piezo actuator 3 is: ■P=V/πma τ7, PXIM...
...(2) C1: Equivalent capacity of the piezo actuator.

The number of times N of charging should be determined so that the voltage at both ends matches or approaches the target charging voltage 100 explained using FIG. 2. For example, as shown in FIG. The microcomputer 5 may be programmed to perform dimensional map interpolation. here,
One-dimensional map data can be obtained experimentally, or (2)
All you have to do is map the expression. In addition, in FIG. 4, the interpolation result is rounded up to make the number of charging times an integer value, but other methods such as rounding can also be considered.

FIG. 5 is a schematic diagram showing the discharge timing calculation means, in which the discharge timing is obtained by performing one-dimensional map interpolation calculation according to the signal from the rotation speed detector 41. As will be described later, the pilot injection amount decreases as the discharge timing advances. The map data used for map interpolation is based on diesel engine compliance standards, so it cannot be generalized, but the higher the rotation, the more important horsepower is than noise, so the discharge timing is advanced to reduce the pilot injection amount. It is desirable to bring it to the side. It goes without saying that the discharge timing may be corrected in accordance with signals from the engine load detector 42, the cooling water temperature detector 43, and the like.

Next, the overall operation of the fuel injection rate control device of this embodiment will be explained with reference to the timing chart shown in FIG. FIG. 6 (al indicates the lift state of the plunger 11. First, when the plunger descends and reaches point 2, reaching a region unrelated to fuel injection, the transistor 62 of the piezo charging means 6
The same figure (b
l) Gradually charge the piezo actuator 3 (charging voltage: ■) Although the number of charging times is 4 in the figure,
This number of times is determined in advance by the means explained using FIG. 4 from the target charging voltage 100 determined by the charging voltage calculation means. After that, when the plunger starts to lift again, the force of the high pressure chamber 12 also increases according to the amount of plunger lift, as shown in FIG. 2(e). At the same time, as shown in FIG. 3(d), the voltage across the piezo actuator 3 further increases due to the electric charge generated by itself. When the pressure in the high pressure chamber 12 becomes equal to or higher than the nozzle opening pressure, injection is started as shown in FIG. After that, when the discharge time determined in advance by the discharge time calculation means is reached (0 point), the transistor 71 of the piezo discharge means becomes "ON" state as shown in FIG. The charge is discharged.

At this time, the piezo actuator 3 contracts by an amount corresponding to the falling voltage v,', the pressure in the high pressure chamber 12 decreases, the injection is temporarily stopped, and a pilot injection is formed as shown in if) of the same figure. Here, based on this principle, it can be seen that if the discharge time (2) is advanced, the pilot injection amount decreases. After that, when the plunger 11 further lifts, the pressure in the high pressure chamber 12 increases again, and injection (main injection) is started. here,
Amount of voltage change during discharge of piezo actuator 3 (VP'
) is larger, the more the piezo actuator 3 contracts, the lower the pressure in the high pressure chamber 12 becomes larger, the second injection is delayed, and the injection stop period becomes longer. Thereafter, the fuel injection is stopped by a governor means (not shown), a main injection is formed, and one fuel injection cycle is completed.

As described above in detail, according to this embodiment, both the injection amount of pilot injection and the injection stop period can be adjusted to optimal values. Furthermore, a noteworthy point in this embodiment is that the piezo actuator 3 is charged in multiple steps. The effect of this will be explained below. The voltage VFI that can be stored in the piezo actuator 3 with one charge is expressed by the following equation.

VPI ” J L / Cp X I s
”...=(310P: Equivalent capacity of the piezo actuator, ■Y: Current flowing through the inductor in advance, L: Inductance of the inductor.

In equation (3), in order to make ■, a high voltage, the current I
It is necessary to increase s or increase the inductance L. In order to increase the currents I and 4, the transistor 62 must be of a high voltage and large current type, making the piezo charging means 6 expensive and large. Furthermore, if the inductance L is increased, the inductor 61 becomes large and expensive.

This is because in order to obtain a large inductance L with a small inductor, it is necessary to make the winding thinner, and in this case, the internal resistance of the inductor cannot be ignored, which not only causes heat generation in the inductor and a decrease in circuit efficiency, but also increases the internal resistance. This is because the predetermined current value (4) may not be obtained. Therefore, in this embodiment, the piezo actuator 3
By dividing charging into multiple times, a relatively small inductor 61 and a relatively small transistor 62 with a small current capacity can be charged.
This realizes the piezo charging means 6.

In this embodiment, the number of times of charging is multiple times means that charging is performed in multiple times when it is desired to make the injection stop period relatively long, that is, when it is desired to make the value of the voltage V relatively large. When the value of the voltage V is small, the small inductor 61 and transistor 62 described above can be sufficiently charged even if the number of times of charging is one, so in this case, the number of times of charging may be set to one. Further, when there is no need to charge the battery in advance, the number of charging times may be set to zero.

Next, other variations for improving the control accuracy of the above embodiment will be explained with reference to FIGS. 7 to 10. In the above embodiment, the transistor 62 of the piezo charging means is turned on.
``Since the state time TON is fixed, when the battery voltage decreases, the inductor current I, 4 after T0 decreases, and the charging voltage of the piezo actuator 3 decreases.

Therefore, the algorithm for calculating the number of charging times N from the target charging voltage 100 explained using FIG. 4 is changed to that shown in FIG.

That is, a battery voltage detector 44 that detects the voltage value of the battery is added as an operating state detection means, and the number of charging times N is determined by the target charging voltage 100 and the battery voltage detector 44.
If it is determined by two-dimensional map interpolation using signals from the battery, the actual charging voltage can be brought close to the target charging voltage 100 regardless of the magnitude of the battery voltage. Of course, the above time T. , may be corrected by the battery voltage.

Also, as a more direct method, actually inductor 61
If the current flowing through the battery is detected by a circuit and the energy of the inductor 61 is transferred to the piezo actuator 3 when this current reaches a predetermined value, charging to a predetermined voltage can be achieved regardless of the battery voltage or the like. Means for this purpose will be explained with reference to FIG. As for the structure, the piezo charging means 6 of FIG. 1 may be replaced with the piezo charging means 6' of FIG. 8.

In the drawings, parts having the same functions are given the same reference numerals, and their explanations will be omitted. 64 is a current detection resistor, which generates a voltage corresponding to the current flowing through the inductor 61 at 21 points. The resistor 65 and the Zener diode 66 create comparison voltages at 22 points. A comparator 67 outputs an "H" level when the inductor current reaches a predetermined value.

6B is an SR flip-flop, which is set by a signal from the microcomputer 5 and is connected to the comparator 67.
It is reset by the "■1" level signal from. As for the operation of the circuit, first, the SR flip-flop 6 is activated by a charging signal with a short pulse width from the microcomputer 5.
8 is set and Q is at "H" level, transistor 6
2 is in the "0N" state. After that, when the current of the inductor 61 reaches a predetermined value, the output of the comparator 67 becomes “H”.
” level, the SR flip-flop 68 is reset, Q becomes L level, and the transistor 62 becomes “O” level.
FF'' state, all the energy stored in the inductor 61 is transferred to the piezo actuator 3, and the piezo actuator 3 is charged.The charging signal from the microcomputer 5 at this time is determined by the algorithm shown in FIG. Only the number of times N charged is output, and the target charging voltage is 10
Charged to 0.

In addition, in the above embodiment, since the charging voltage of the piezo actuator 3 is adjusted only by the number of charging times N, it is naturally difficult to change the charging voltage continuously, and it is difficult to change the charging voltage continuously when fine-grained pilot injection control is required. is not desirable. Therefore, the means to solve this problem is shown in Fig. 9(a).
This will be explained along with FIGS. 10(b), 10(c), and FIG. FIG. 9 is a timing chart showing the operation of the piezo charging means 6. The difference between FIG. 9 and FIG. 3 is that the transistor 62 “
ON” state time is time T at the final time. Time T shorter than N
. This is the point N'. This time T. By continuously setting N' from O to TON, the piezo charging voltage can be adjusted as desired. At this time, the transistor 62
"ON" state time T. , l, and the final "ON" state time T. How to determine 8 will be explained with reference to FIG. First, as in the case of FIG. 4, the number of times n of charging is determined by one-dimensional map interpolation using the target charging voltage 100. However, in this case, the number of times n of charging is kept as a real value without rounding up or converting it into an integer as explained in FIG. 4.

Then, the integer part of this charging number n is the "ON" state time T of the transistor 62. , l, and the fractional part of is Δn, 'l'0. '=ΔnXTo,.

By T. Determine H'. In this way, the piezo charging voltage 100 can be set continuously. In addition, time T. H′
is not limited to the final round, but may be any other round.

Although the embodiment shown in FIG. 1 and other variations have been shown above, the present invention is not limited thereto and can be modified in various ways without departing from the spirit thereof.

Needless to say, the object to be controlled is only the injection stop period, and therefore, in the above embodiment, the microcomputer 5 does not have to have the function of the discharge timing calculation means of the present invention, and the piezoelectric The time at which the electric charge generated in the actuator 3 is discharged may be fixed at an appropriate time after the piezo actuator 3 is charged in advance.

〔Effect of the invention〕

As detailed above, according to the fuel injection rate control device of the present invention, the piezo actuator is actuated to realize pilot injection by the injection pump, and according to the first invention, the piezo actuator is actuated in response to a signal from the operating state detection means. By adjusting the amount of electric charge to be charged in advance, the injection stop period can be adjusted to always optimize the operating condition of the diesel engine. By adjusting the amount of charge pre-charged to the piezo actuator and the timing at which the piezo element itself discharges the entire amount of charge, including the amount of charge generated when it receives pressure in the pump high-pressure chamber, the injection stop period can be adjusted to reduce the amount of charge during diesel engine operation. The conditions can always be adjusted to the optimum, and furthermore, the pilot injection amount can be set to an appropriate value.

Therefore, the present invention has the excellent effect of improving the ignitability of fuel during main injection and reducing noise and vibration during idling of a diesel engine.

Furthermore, by charging the piezo actuator multiple times, there is an effect that the circuit scale of the piezo charging means can be made relatively small.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the fuel injection rate control device of the present invention, FIG. 2 is a schematic explanatory diagram of charging voltage calculation means, and FIG.
The figure is a timing chart explaining the operation of the piezo charging means, FIG. 4 is a schematic explanatory diagram showing the configuration for calculating the number of charging times from the target charging voltage, FIG. 5 is a schematic explanatory diagram of the discharge timing calculating means, and FIG. FIG. 1 is a timing chart explaining the operation of the embodiment, FIG. 7 is a schematic explanatory diagram showing another configuration diagram for calculating the number of charging times from the target charging voltage, and FIG. 8 is a diagram showing another example of the piezo charging means. The circuit diagram, FIG. 9 is a time chart explaining the operation of the piezo charging means when the charging voltage is set to a continuous value, and FIG. 1θ is the number of times of charging from the target charging voltage and the time T in FIG. 9. FIG. 2 is a schematic explanatory diagram showing a configuration for calculating H'. 1... 1t pump, 3... Piezo actuator. 4... Operating state detection means, 5... Microcomputer, 6.6'... Piezo charge means, 7... Piezo discharge means, 12... High pressure chamber, 61... Inductor.

Claims (4)

[Claims] (1) a piezo actuator installed facing the high pressure chamber of the fuel injection pump; an operating state detecting means for detecting the operating state of the diesel engine and detecting at least the rotational speed of the diesel engine; and the operating state Charging voltage calculation means for calculating a voltage value to charge the piezo actuator according to a signal from the detection means; Piezo charging means for charging the piezo actuator to the voltage value calculated by the charging voltage calculation means; and a predetermined time. and piezo discharge means for discharging the electric charge generated in the piezo actuator. (2) The piezo charging means once passes current through the inductor, charges the piezo actuator with the energy stored in the inductor, and charges the piezo actuator multiple times in one cycle of fuel injection. A fuel injection rate control device according to claim 1, characterized in that: (3) a piezo actuator installed facing the high pressure chamber of the fuel injection pump; an operating state detection means for detecting the operating state of the diesel engine, and detecting at least the rotational speed of the diesel engine; and the operating state charging voltage calculation means for calculating a voltage value to charge the piezo actuator according to a signal from the detection means; piezo charging means for charging the piezo actuator to the voltage value calculated by the charging voltage calculation means; Discharge time calculation means for calculating a discharge time for discharging the charge generated in the piezo actuator according to a signal from the state detection means; and piezo discharge means for discharging the charge generated in the piezo actuator at the discharge time. A fuel injection rate control device characterized by: (4) The piezo charging means once passes a current through the inductor, charges the piezo actuator with the energy stored in the inductor, and charges the piezo actuator multiple times in one cycle of fuel injection. The fuel injection rate control device according to claim 3, characterized in that: